Compass-correcting device.



No. 769,870. PATENTED SEPT. 13, 1904 F. MORRISON.

COMPASS CORRECTING DEVICE.

APPLIOATION FILED MAR.16. 1903.

N0 MODEL.

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UNITED STATES Patented September 13, 1904.

PATENT OEEicE.

FRANK MORRISON, OF CLEVELAND, OHIO.

COMPASS-CORRECT! NG DEVICE.

SPECIFICATION forming part of Letters Patent No. 769,870, dated September 13, 1904,

Application filed March 16, 1903.

To a whom it may concern:

Be it known that I, FRANK MORRISON, a citizen of the United States of America, residing at Cleveland, in the county of Ouyahoga and State of Ohio, have invented certain new and useful Improvements in Compass-Correcting Devices; and I hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it pertains to make and use the same.

This invention relates to improvements in compasses.

The object of this invention is to provide means for correcting the variations in a compass caused by the proximity of bodies which exert a magnetic force or influence on the needle, tending to divert or draw the needle from its true positionrelative to the magnetic poles of the earth.

My invention therefore consists in providing means for supporting one or more cor.- recting-magnets on the bowl of the compass, so that the changes in position of the compass-bowl as it swings on its supports will but slightly change the relative positions of the correcting-magnets and the needle of the compass, and therefore the force exerted by the correcting-magnets on the needle will be approximately constant.

My invention furtherconsists in providing means for adjusting the magnets on the compass-bowl so as to increase or decrease the influence of the correcting magnets on the needle.

My invention also consists in the features of construction and combination of parts, as illustrated in the drawings and hereinafter described in the specification and pointed out in the claim.

In the accompanying drawings, Figure l is a top plan of a compass provided with my improved device. Fig. 2 is a section on line 2 2, Fig. 1. Fig. 3 is a section on line?) 3, Fig. 2. Fig. t illustrates two sizes of correcting-magnets used in my device.

Again referring to the drawings, a represents the bowl of the compass, in which the needles 6 are mounted in the usual manner. The bowl (0 is mounted so as to swing verti- Serial No. 147,979. (No model.)

rim of thebowl a of the compass is arranged a collar 6, preferably formed of spun brass, in order that it may be light and thin, so as not to interfere in any way with the movement of the bowl in its regular mounting. In this collar 0 are formed a number of screwho'les e. In the rim of the bowl (0 are formed series of screw-holes a, and by turning the collar 6 on the rim of the bowl 0 the screwholes 6' can be made to register with the holes a, and the collar can thus be adjusted circumfe'rentially on the bowl a of the compass. Screws 0 are provided for securing the col lar e on the bowl (6. On the collar 0 are arranged three plates f, preferably ninety degrees apart, on each of which is mounted a vertical frame comprising two posts f and f 2 and a cross-plate f. In each frame is arranged an endless screw f", secured in bearings in the plates f and f The end of the screw f which projects through the plate f is preferably squared, as. at so that it may be engaged by a key or other device for turning it.

A bracket 9, which is provided with a screwthreaded bore g, corresponding to the screw f, is arranged on each of the said screws ff so as to travel up and down thereon when the screw is turned in one direction or the other. A screw g is provided for locking the bracket 9 on the screw f". To each bracket g is secured a small horizontally-arranged tube g the ends of which are closed by means of caps 9 which are preferably arranged to screw on the respective ends of the tube. Each of the tubes g forms a receptacle for holding one or more correcting-magnets n. These correcting-magnets are graded according to their magnetic strength, so that by properly selecting one magnet or grouping two or more magnets and placing them in a tube g any desired degree of magnetic influence or strength can be obtained.

A weight it is preferably secured on the collar 6 opposite the central plate f, so as to balance the bowl.

The operation of this device is as follows:

The collar 6 is first adjusted on the rim of the bowl of the compass, preferably in such a position that the central receptacle for the corrccting-magnets will be perpendicular to the needles when the needles are in their true north and south positions, and the other two receptacles will then be parallel with the needles. After the compass has been mounted in its proper position on the vessel the bow thereof is pointed to the north, and the compass is then corrected for the north. This is accomplished by trying different grades of magnets in the receptacle until the north poles of the needles are approximately brought to their true position. After the proper magnets have been placed in the receptacle the receptacle can be adjusted vertically, so as to increase or decrease the influence exerted by the magnets within the receptacle on the needles of the compass, thereby making it possible to complete the correction with the greatest accuracy. When the compass has been corrected for the north, the vessel is turned so that the bow thereof points to the west, and the compass is corrected for the west in a similar manner, after which the vessel is turned so that the bow points toward the east, and the compass is corrected for the east in the same way.

What I claim is The combination with the bowl of a compass, of a collar arranged to encircle the rim of said bowl, frames arranged on said collar, endless screws mounted in said frames, brackets arranged on said screws so as to be actuated by the rotation of said screws, tubessecured to said brackets, magnets arranged in said tubes and means for closing the ends of said tubes, substantially as described and for the purpose set forth.

In testimony whereof I sign the foregoing specification, in the presence of two witnesses, tOhlis 10th day of March, 1908, at Cleveland,

FRANK MORRISON.

Witnesses:

VICTOR O. LYNCH, G. M. HAYES. 

